Eric Ravenscraft

Whether you're buying a house, getting a new a car, or moving to a more expensive area, it's tempting to assume you can handle the increased expenses. Prove it to yourself by taking the difference and saving it for three months first.

Financial expert and author Denise Winston suggests that, before making a major change that will raise your expenses, you should spend at least three months saving the same amount you would be spending. That way, you have a pretty good idea of what life would be like when you make the switch.

If you're upgrading your lifestyle — say going from $1,000 in rent to a $1,500 mortgage payment, put the extra $500 in a savings account," suggests Winston. "You'll soon know if you can afford the extra amount each month."

Another big benefit of putting away this extra money: You'll be contributing even more to the down payment on whatever biggie item you're purchasing. "It'll be a great feeling to have that $1,500 you saved to help close the transaction," she says.

Obviously this assumes that you can spend that much time, which isn't always the case. Sometimes your lease ends right as you get a raise, or your car breaks down at the wrong time (read: any time). Still, if you have the option, it's best to give yourself a trial run first.